The four polite verb endings
You can use time and negation to identify the full polite verb ending and produce it in a short sentence.
Project lessons 06, 07, and 08; time words from lessons 12–14 help but are not required.
The final verb block combines two choices: non-past or past, and affirmative or negative. ます can express a habit or a plan and does not automatically mean that an action is happening now.
毎日、本を読みます。
明日、本を読みません。
昨日、本を読みました。
昨日、本を読みませんでした。
Start with 毎日、本を読みます。 Keep the object and verb constant and change the time anchor and ending across four minimal contrasts.
Using ません with 昨日 when past negative is intended.
Adding です after a complete ます verb.